Extensive studies on transfer of radionuclides to animals were carried out in the USSR from the 1950s. Few of these studies were published in the international refereed literature or taken into account in international reviews. This paper continues a series of reviews of Russian language literature on radionuclide transfer to animals, providing information on biological half-lives of radionuclides in various animal tissues. The data are compared, where possible, with those reported in other countries. The data are normally quantified using a single or double exponential accounting for different proportions of the loss. For some products, such as milk, biological half-lives tend to be rapid at 1-3 d for most radionuclides and largely described by a single exponential. However, for other animal products biological half-lives can vary widely as they are influenced by many factors such as the age and size of the animal. Experimental protocols, such as the duration of the study, radionuclide administration and/or sample collection protocol also influence the value of biological half-lives estimated.